We study the rates of tidal disruption of stars on bound to unbound orbits by intermediate-mass to supermassive black holes using high-accuracy direct N-body experiments. Stars from the star cluster approaching the black hole can have three types of orbit: eccentric, parabolic, and hyperbolic. Since the mass fallback rate shows different variabilities depending on the orbital type, we can classify tidal disruption events (TDEs) into three main categories: eccentric, parabolic, and hyperbolic. The respective TDEs are characterized by two critical values of the orbital eccentricity: the lower critical eccentricity is the one below which stars on eccentric orbits cause finite, intense accretion, and the upper critical eccentricity is the one above which stars on hyperbolic orbits cause no accretion. Moreover, we find that parabolic TDEs can be divided into three subclasses: precisely parabolic, marginally eccentric, and marginally hyperbolic. We analytically derive that the mass fallback rate of marginally eccentric TDEs can be flatter and slightly higher than the standard fallback rate proportional to t(-5/3), whereas it can be flatter and lower for marginally hyperbolic TDEs. We confirm using N-body experiments that only a few eccentric, precisely parabolic, and hyperbolic TDEs can occur in a spherical stellar system with a single intermediate-mass to supermassive black hole. A substantial fraction of the stars approaching the black hole would cause marginally eccentric or marginally hyperbolic TDEs.

项目资助者

Korea Astronomy and Space Science Institute (KASI) under the RD program
; Basic Science Research Program through the National Research Foundation of Korea (NRF) - Ministry of Education(NRF-2017R1D1A1B03028580)
; Chinese Academy of Sciences (CAS) through the Silk Road Project at NAOC, through the CAS Visiting Professorship for Senior International Scientists(2009S1-5)
; Chinese Academy of Sciences (CAS) through the "Qianren" special foreign experts programme of China
; National Natural Science Foundation of China(NSFC 11603067, 11303039, 11673032)
; NASU under the Main Astronomical Observatory GRID/GPU computing cluster project
; Ministry of Finance of the People's Republic of China(ZDYZ2008-2)
; Strategic Priority Research Program (PilotB) "Multi-waveband Gravitational Wave Universe" of the CAS(XDB23040100)